1. Field of the Invention
This invention pertains to the control of gripper arms, and particularly the control of gripper arms suitable for use with insertion machines and the like.
2. Prior Art and Other Considerations
Gripper arms have long been used with insertion machines of the type depicted in U.S. Pat. No. 2,325,455 to A. H. Williams which is incorporated herein by reference. Prior art gripper arms typically each have fixed and movable jaw members. The fixed jaw member is usually integral with the gripper arm while the movable jaw is selectively operated so that articles, such as documents or inserts, can be engaged between and released from the two jaws.
Prior art gripper arms have traditionally been mounted on two elongated shafts which extend above and along an insert transport track or raceway. The first or upper shaft, which oscillates once per machine cycle, has an upper portion of the gripper arm keyed thereto so that the gripper arm oscillates toward and away from a corresponding insertion supply station in timed relationship with the other operations occuring at the station. The second shaft also oscillates once during each machine cycle to actuate the movable jaw member into and out of engagement with the fixed jaw member in timed relationship with the oscillation of the gripper arm about the first shaft and with the rest of the machine. A cam keyed to the second shaft acts upon a connecting rod which in turn moves the movable jaw member away from the fixed jaw member against the action of a tension spring. The jaws are held apart in this manner until the gripper arm is oscillated toward the corresponding insertion station whereat the movable jaw is positioned above and the fixed jaw is positioned below an insert. The second shaft then oscillates to close the movable jaw against the fixed jaw to engage and grip the insert. The first shaft thereupon swings away from the insert station, pulling the selected insert therefrom in a direction toward the insert track. Over the insert track the second shaft is oscillated to move the movable jaw member away from the fixed jaw and thereby release the insert, permitting the insert to fall onto the transport track.
Although only one gripper arm structure has been described above, it should be understood that a plurality of gripper arms are provided with an insertion machine, each gripper arm being positioned in relation to corresponding insert stations linearly arranged along an insert track. Insertion machines of this type described above can operate through a range of speeds. An operator may at a lower end of the operational speed range "step" or "jog" the machine through a machine cycle at a very slow speed as is useful in the case of setting up the machine with new material. At high operational speeds the insertion machine may operate at a rate in the neighborhood of 10,000 cycles per hour.
In setting up an insertion machine, the operator must be cognizant of the fact that each insert must be released at a precise location along the insert track, usually within 1/8 inch of a specified precise location. In this respect, each insert must be released so that the insert contacts both of a pair of pusher pins that index the insert down the insert track. The time delay associated with the actuation of the movable jaw member thus becomes a factor in determining where on the insert track the insert will be released.
If the delay time in actuating the movable jaw member is constant regardless of the operational speed of the machine, significant error can occur in placement of the insert on the insert track. For example, a delay of 20 to 25 milliseconds in actuating the movable jaw member when the insertion machine is operating at 10,000 cycles per hour results in the gripper arm travelling approximately one inch. Thus, a give magnitude of time delay in actuating the movable jaw member in the jog mode or at low speed is not suitable for higher operational speeds and can, when the machine is operated at higher speeds, result in significant misplacement of the insert on the insert track. In this respect U.S. patent application Ser. No. 06/648,391, filed Sept. 7, 1984 by Vandersyde et al., and incorporated herein by reference, addresses the foregoing problem by providing a solenoid actuated gripper arm wherein the magnitude of delay involved in actuating a movable jaw member is related to the operational speed of the insertion machine in conjunction with which the gripper arm is employed.
The operational speed of an insertion machine is but one factor which is pertinent to the timing of the actuation of gripper arm jaw members and hence the proper placement of inserts on an insert track. Another factor affecting the timing of the release of inserts at proper positions on the insert track is the size of the inserts. In this regard, it is desirous that each gripper arm release its inserts so that each insert will be contacted by both advancing pusher pins on the insert track. When the size of inserts vary from insert station to insert station, and when all the gripper arms associated with the insert stations along an insert track are actuated to release their inserts at the same point in a machine cycle, an insert of an odd size may be released and deposited on the insert track in a manner whereby it cannot contact both of its pusher pins. The prior art manner of essentially simultaneously releasing inserts from the various stations regardless of insert size can ultimately result in skewed insert placement, which in turn can cause jamming on the insert track.
The insert tracks or raceways of many conventional insertion machines have side rails or the like which extend on opposite sides of the insert track and substantially along the length (i.e. the major dimension or direction of travel) of the insert track. In many insertion machines the positioning of one or both of these side rails is adjustable so that the distance separating the side rails can be selectively varied. In some insertion machines, for example, the side rail nearest from the row of insert stations can be moved through a displacement range of as much as four inches while the side rail furtherest the row of insert stations can be moved through a displacement range of as much as three-quarters of an inch. The selective adjustment of the side rails advantageously permits the insertion machine to accommodate on its insert track inserts of varying size. For example, if the size of the inserts vary from insert station to insert station, the side rails can be positionally adjusted sufficiently far apart so that the largest of the inserts at the various insert stations can be accommodated on the insert track.
In order to accommodate the very large size inserts that might be present at one of the insert stations, an operator typically first moves the side rail furtherest from the row of insert stations to its maximum displacement. If the insert track is still not wide enough the operator can then move the side rail nearest the row of insert stations closer to the insert stations to further broaden the insert track. While the selective positional adjustment of the side rails advantageously permits the insertion machine to accommodate on its insert track inserts of varying and especially large size, in a sense this adjustment capability is also a mixed blessing in that it further complicates the precise positioning of inserts on the insert track.
In view of the foregoing, it is an object of the present invention to provide method and apparatus for controlling the actuation of individual gripper arms of an insertion machine to take into consideration the fact that insert sizes may differ from insert station to insert station.
An advantage of the present invention is the provision of method and apparatus for simultaneously adjusting the timed actuation of a plurality of gripper arms of an insertion machine to take into consideration the selective positional adjustment of side rails bordering the insert track.
A further advantage of the present invention is the provision of method and apparatus whereby timing of insert release from each gripper arm can be individually adjusted.
Another advantage of the present invention is the provision of embodiments wherein the magnitude of delays involved in actuating movable jaw members is related to the operational speed of the insertion machine in conjunction with which gripper arms are employed.
Yet another advantage of the present invention is the provision of method and apparatus for fine tuning even during machine operation the insert release times of individual gripper arms of an insertion machine.